Radiation-curable polymers containing pendant unsaturated peptide groups derived from azlactone polymers

ABSTRACT

A composition comprising a radiation-curable polymer, said polymer being crosslinkable and having pendant ethylenically unsaturated peptide groups is disclosed. Such polymers are useful in the field of graphic arts.

FIELD OF THE INVENTION

This invention relates to energy-sensitive polymers which may, forexample, be radiation sensitive and electron beam sensitive. Thesepolymers may be useful in imaging systems such as are used in graphicarts.

DESCRIPTION OF THE PRIOR ART

Energy-sensitive materials have been used in the field of graphic artsfor many years. For such materials to function effectively, it isdesirable that the energy sensitive composition comprises a polymerwhich crosslinks and becomes insoluble in developing solvents onexposure to radiation yet remains soluble in unexposed areas.Furthermore, it is desirable for maximum production efficiency that theperiod of exposure to radiation be as short as possible. It is alsohighly desirable that this exposure to actinic radiation occur in anormal air environment to obviate the need for blanketing the reactionwith an inert gas such as nitrogen or using an oxygen impermeable topcovering in order to overcome the well-known polymerization inhibitingeffects of oxygen. A still further requirement is that in theradiation-exposed areas extensive crosslinking in the polymer shouldoccur so that the exposed areas will not swell when the article issubsequently treated with a solvent to dissolve away the still soluble,non-exposed areas.

In the attempt to solve these and other problems apparent to one skilledin the art, resort has been made to utilize polymers havingacrylic-functional groups at the ends of the polymer or pendant to thechain of the polymer. The polymer art is replete with descriptions ofpolymers having two terminal acrylic-functional groups, examples ofwhich are U.S. Pat. Nos. 3,297,745 and 3,700,643 wherein a polymerformed by the reaction of a diol with two equivalents of a diisocyanatefollowed by reaction with a hydroxyalkyl acrylate monomer is described.Such polymers with terminal acrylic-functionality generally have acuring rate that is slower and a concentration of acrylic-functionalitythat is lower than is desirable for use in a negative workingenergy-sensitive element.

Polymers having a multiplicity of pendant acrylic-functional groups,because of the generally greater number of reactable acrylic groups,have faster curing rates, better curing rates in the presence of oxygen,i.e. in air, and higher crosslink density in the exposed, cured regionswhich results in better overall resistance to swelling by the developingsolvent. U.S. Pat. No. 3,448,089 describes two methods for preparingpolymers having pendant acrylic-functional groups. In one of thesemethods, interpolymers containing pendant epoxy groups are prepared byinterpolymerization of, for example, glycidyl acrylate with other freeradically polymerizable monomers. The acrylic-functionality is impartedto the interpolymer by a ring opening reaction with acrylic acid. Thisring opening reaction, however, requires prolonged reaction times andhigher temperatures, e.g. 15 hours in refluxing methyl ethyl ketonesolvent. Such stringent reaction conditions are undesirable and canresult in premature and inadvertent gelation and cross-linking of theinterpolymer. In the other method, interpolymers having pendantcarboxylic acid anhydride groups are first prepared byinterpolymerization of maleic anhydride, for example, with suitable freeradically polymerizable monomers. The interpolymer is then madeacrylic-functional by subsequent reaction with a hydroxyalkyl acrylatemonomer. While this method permits functionalization at moderatetemperatures, its use is limited because polymers generally aredifficult to obtain with maleic anhydride and intermonomers other thanstyrene and vinyl ethers. Furthermore, since a carboxylic acid group isalso formed when the hydroxyalkyl acrylate monomer reacts with thependant anhydride group, the polymer becomes quite water sensitive andadhesion to certain desired substrates can suffer even in onlymoderately humid environments. Special precautions such asesterification of the carboxyl group must be taken. These precautionsnecessitate prolonged and involved reaction conditions that add cost tothe procedure.

In contrast to the above-mentioned art and its inherent problemsinvolving acrylic-functional groups, the present invention relates toenergy-sensitive polymers capable of rapid curing under mild conditionseven in the presence of air. These polymers have pendant ethylenicallyunsaturated units secured to the polymer backbone through peptide groups(hereinafter referred to as "polymers having pendant ethylenicallyunsaturated peptide groups"). By peptide group is meant a group havingat least one ##STR1## unit, which unit is derived from an amino acid ofthe general formula ##STR2## in which R is an aliphatic radical. Thepolymers may be prepared, as described below, from ethylenicallyunsaturated azlactone polymers having pendant azlactone groups(4,4-disubstituted-2-oxazolin-5-ones and higher homologues aredesignated "azlactone" hereinafter).

Reactions of azlactone compounds with nucleophilic compounds aredescribed in the literature, as for example by an article by R. Filler,Advances in Heterocyclic Chemistry, Vol. 4, pps. 75-106, A. R.Katritzky, Ed., Academic Press, New York, 1965. There is no apparentdiscussion of the preparation of energy-curable vinyl polymers fromazlactones.

Coatings comprised of diols or diamines and copolymers of 2-alkenyl or2-acryloyloxyalkyl azlactones and olefinically unsaturated monomers aredisclosed in U.S. Pat. No. 3,583,950. Crosslinking is accomplished byheating the coating such that the diol or diamine will cause azlactonering-opening reactions to occur on two polymer chains. Polymers of thatpatent are not radiation-curable.

Also, coatings of copolymers of 2-alkenyl- or 2-acryloxyalkyl azlactoneswith acrylic acid esters and copolymerizable vinylidene compounds havingat least one hydroxyl group which crosslink on drying or mild heatingare described in U.S. Pat. Nos. 3,488,327 and 3,598,790. Such polymerscrosslink by reaction of hydroxyl groups on one chain of the polymerwith azlactone groups on other chains. There is no teaching in thesepatents of polymers having pendant polymerizable ethylenicallyunsaturated groups.

U.S. Pat. No. 3,511,894 describes a process for making graft polymers by(1) preparing a macromolecule to be grafted, so that it contains pendantazlactone groups, (2) reacting this polymer with an azo group-containingnucleophilic compound to form a macromolecule having polymer-bound azogroups, and (3) heating the azo group-containing macromolecule toliberate nitrogen and form free radical sites on the macromolecule whichradicals initiate polymerization of grafting monomer added thereto. U.S.Pat. No. 3,948,866 also discloses graft polymers for use as specialstabilizing agents for the suspension-type polymerization of watersoluble polymers. A number of processes are described in this patent forthe preparation of suitable graft polymers, among them being a processhaving the steps of (1) preparing a copolymer having a reactive group,(2) forming an interpolymer having pendant double bonds by reacting thereactive group-containing copolymer with a compound having both acomplementary reactive group and a double bond that can be polymerized,and (3) causing free radical polymerization of graft monomers to takeplace in the presence of the copolymer having pendant double bonds toform the graft polymer. It should be noted that patentee discloses onlygraft polymers, and, furthermore, he does not recognize theradiation-polymerizing and crosslinking potential of some of thehypothesized interpolymers. Patentee broadly states that the preparationof copolymers from, among other possibilities, interpolymers containingazlactone groups with compounds containing complementary reactive groupsand a double bond is well known in the art. The present inventors havefound no references in the scientific or patent literature tosubstantiate this statement. In addition, polymers disclosed by patenteeare further reacted with the grafting monomers only in a solvent takingadequate precautions to remove oxygen from the system with the finalproduct remaining soluble in said solvent, whereas, as will be discussedbelow, those polymers of the present invention are intended to be castfrom solution and then intended to be insolubilized or crosslinked.Furthermore, we have found that the polymers are able to beinsolubilized even in the presence of oxygen when derived from azlactoneinterpolymers containing greater than about 25 weight percent of theazlactone moiety.

SUMMARY OF THE INVENTION

The present invention provides compositions which areradiation-crosslinkable. These compositions may be applied to substratesto provide imaging systems or radiation curable binders and protectivelayers. These materials may have fast cure rates, insensitivity tooxygen and appreciable resistance to swelling by common solvents. Thesepolymers, which can be cured rapidly even in the presence of air, havependant ethylenically unsaturated (especially acrylic) peptide groups.The present invention further relates to a novel, rapid, efficientprocess for preparing these polymers and copolymers in the reaction ofnucleophilic compounds having an ethylenically unsaturated group withpolymers containing azlactone groups.

The energy-sensitive polymers of the present invention, which cure tocrosslinked, insoluble polymers, are represented by substances V and VIin an overall process for preparing these radiation-curable polymers. Asummary of these steps is as follows: ##STR3##

The present invention discloses the novel polymers designated V and VIand the method of their preparation, i.e. steps IV to V and V to VI.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention, energy-sensitive polymershaving pendant ethylenically unsaturated peptide groups are disclosed.The structure below is not intended to show polymers with only M unitson one side and only units of the formula ##STR4## on the other side.The following structure should be read as indicating that the two typesof units alternate in various random patterns throughout the polymer:##STR5## wherein

M is a copolymer unit derived from one or more monomers (e.g. any freeradically polymerizable, ethylenically unsaturated monomer except thoseof the HXA type, because HXA type monomers cause an undesirable,premature insolubilization of the interpolymer, discussed in detailbelow) interpolymerizable with the ethylenically unsaturated azlactonemonomer (III);

R¹ is hydrogen or methyl;

R² is selected from a single bond, --R³ --, and ##STR6## in which R³ isalkylene having 1 to 12 carbon atoms, preferably 1 to 6 carbon atoms,and W is --O--, --S-- or --NH--;

R⁴ and R⁷ are independently selected from a single bond and methylene,or substituted methylene having 1 to 12 carbon atoms; R⁵ and R⁶ areindependently alkyl or cycloalkyl having 1 to 12 carbon atoms, aryl oraralkyl having 6 to 12 carbon atoms or R⁵ and R⁶ taken together with thecarbon to which they are joined form a 5-- or 6--membered carbocyclicring, or may be H when at least one of R⁴ and R⁷ is methylene;

n is 1, 2 or 3;

X is --O--, --NH-- or --S--;

A is a polymerizable, ethylenically unsaturated group selected from

(a) ##STR7## in which R⁸ is an alkylene group having 1 to 12 carbonatoms, an arylene group having 6 to 10 carbon atoms, or an oxyalkylenegroup, --OR)_(p) in which R is a lower alkylene group having 2 to 4carbon atoms and p is 1 to 4; R⁹ and R¹⁰ are independently hydrogen, andalkyl group having 1 to 12 carbon atoms, or an aryl group having 6 to 10ring positioned carbon atoms wherein aryl is defined as a phenyl ornaphthyl moiety optionally having substitution thereon or

(b) --R⁸ --WY in which R⁸ is as defined under the definition for A, W asdefined under the definition for R², and Y is an ethylenicallyunsaturated group selected from the group including acryloyl,methacryloyl, cinnamoyl, maleoyl, fumaroyl, itaconoyl and crotonoyl andis preferably acryloyl or methacryloyl;

a and b are independent whole integer numbers, and b is at least 1,sufficient to provide the polymer with a weight percent of M units inthe azlactone-containing interpolymer between about 0 and 90, preferably0 and 75.

These energy-sensitive polymers of the invention are prepared by thereaction (conditions of the reaction are given below) of anethylenically unsaturated nucleophilic compound, HXA, with the azlactonegroup of a polymer having pendant azlactone groups, which polymer(designated "azlactone polymer") is known in the art and consistsessentially of 10 to 100 percent, preferably 25 to 100 percent, and mostpreferably 30 to 100 percent, by weight of units from one or moreethylenically unsaturated azlactone monomers and 90 to 0 percent,preferably 75 to 0 percent, and most preferably 70 to 0 percent, byweight of one or more vinyl monomers (designated intermonomers)interpolymerizable with the ethylenically unsaturated azlactone monomerin accordance with the equation: ##STR8## wherein M, R¹, R², R⁴, R⁵, R⁶,R⁷, X , A, a and b are defined above for formula V, and n=1.

The preferred compositions of the invention are polymers of Formula Vwhich are radiation curable in the presence of air. Such polymers becomecurable in air when they are derived from polymers containing greaterthan about 25 weight percent of azlactone monomer units. Polymers ofFormula V containing less than about 25 weight percent of units derivedfrom azlactone monomers are useful however, provided they are exposed toradiation in a nitrogen-blanketed atmosphere, discussed below underExample 2.

The HXA compounds are essentially any polymerizable, ethylenicallyunsaturated heteroatomic nucleophile containing an active hydrogen atom;these "active hydrogen" compounds are often referred to as Zerewitinoffcompounds (cf. Kharasch and Reinmuth, Grignard Reactions of NonmetallicSubstances, pps 1166-1198, Prentice-Hall, Inc., Englewood Cliff, N.J.,1954). Suitable examples of HXA compounds are selected from thefollowing classes of heteroatomic Zerewitinoff compounds:

Alcohols: including mono-hydroxyalkyl derivatives of α,β-unsaturatedcarboxylic acids such as 2-hydroxylethyl acrylate, 2-hydroxyethylmethacrylate, 3-hydroxypropyl acrylate, 3-hydroxybutyl acrylate,pentaerythritol triacrylate, trimethylolpropane dimethacrylate,N-(2-hydroxyethyl)acrylamide, 2-hydroxyethyl cinnamate,N-(2-hydroxyethyl)maleimide, methyl 2-hydroxyethyl fumarate, methyl2-hydroxyethyl itaconate, methyl 2-hydroxyethyl maleate, polyoxyethyleneglycol monoacrylate, polyoxypropylene glycol monomethacrylate, and thelike; hydroxy-functional vinyl aromatic monomers such as4-(2-hydroxyethyl)styrene, 4-(3-hydroxyethyl)-1'-methylstyrene, and thelike; hydroxy-functional allylic monomers such as allyl alcohol,methallyl alcohol, diallyl 4-(2-hydroxyethyl)-o-phthalate, and the like;hydroxy-functional vinyl ethers such as 2-hydroxyethyl vinyl ether,4-hydroxybutyl vinyl ether, and the like; and higher ethylenicallyunsaturated alcohols such as 9-octadecen-1-ol, and the like.

Primary amines: including amino-functional allylic compounds such asallyl amine, allyl 4-aminobenzoate, and the like; amino-functional vinylethers such as 2-aminoethyl vinyl ether, 4-aminobutyl vinyl ether, andthe like.

Mercaptans: including mercaptoalkyl derivatives of α,β-unsaturatedcarboxylic acids such as 2-mercaptoethyl acrylate,N-(4-mercaptobutyl)acrylamide, and the like; mercapto-functional vinylaromatic monomers such as 4-vinylthiophenol and the like;mercapto-functional allylic monomers such as allyl mercaptan and thelike; mercapto-functional vinyl ethers such as 2-mercaptoethyl vinylether and the like.

The acrylic- and methacrylic-functional HXA compounds are generallypreferred because of their availability and because of the increasedrate of cure that they provide to the peptide group-containing polymerscompared to the other polymerizable moieties listed above.

Reaction of the azlactone polymers and the HXA compound is convenientlyaccomplished by the addition of the HXA compound directly to a solutionof the polymer or interpolymer. No additional ingredients are requiredfor the primary amine HXA compounds, but catalysts are required for thereaction to proceed at a reasonable rate at room temperature with thealcohol and mercaptan HXA compounds. While the literature discloses thatwhen the azlactone ring is to be opened with methanol or ethanol, forexample, this is best accomplished using refluxing conditions inaddition to Bronsted acid catalysts such as p-toluenesulfonic acid orphosphoric acid and tertiary amines, we have discovered that the abovecatalysts, as well as other Lewis acids, such as BF₃ etherate, AlCl₃,SnCl₄ and TiCl₄ function effectively as catalysts for the reaction atambient temperatures. The progress of the ring-opening reaction can beconveniently followed by recording the infrared spectrum of the reactionmixture and observing the disappearance of the carbonyl stretchingabsorption at about 5.4 microns.

Referring back to U.S. Pat. No. 3,948,866 discussed above, patenteealludes to azlactone polymers to which are grafted complementary doublebond-containing monomers. Patentee does not characterize in any way theresulting copolymers, but he does state that an object of his inventionis the avoidance of crosslinking. In contrast to this prior art, thepresent invention discloses polymers having pendant ethylenicallyunsaturated peptide groups, the purpose of which is to undergo extensivecrosslinking to form insoluble polymers wherein at least 10% of theethylenically unsaturated peptide groups have undergone the radiationinduced crosslinking reaction.

Preparation of polymers of Formula V wherein n=2 or 3 will be discussedbelow.

The polymers of Formula V having pendant ethylenically unsaturatedpeptide groups are "energy curable" to insoluble resins designated as VIabove. By "energy curable" is meant the property of undergoing acrosslinking insolubilizing reaction when exposed to activatingradiation. The activating radiation can be either thermal,electromagnetic (e.g. visible or ultraviolet) or ionizing (e.g. highenergy electrons). An excellent discussion of these different forms ofactivating radiation can be found in W. J. Moore's text entitledPhysical Chemistry (3rd edition, Prentice-hall, 1964, page 819).

When electromagnetic activating radiation is utilized, the procedure isoften termed "photopolymerization". "Photopolymerization" can be dividedinto two fundamental classes, both of which are operative in theinvention:

Class A:

These are photopolymerization reactions of certain ethylenicallyunsaturated compounds in which electromagnetic radiation is required forthe propagation of the polymer-forming or crosslinking reaction tooccur. Examples of polymerizable functional groups which undergo "ClassA" reaction are cinnamoyl and maleimide groups.

Class B:

These are often termed "photoinitiated polymerizations" because theelectromagnetic radiation is only necessary for initiation of thepolymer-forming or crosslinking reaction to occur. Essentially all ofthe polymerizable functional groups with the exception of cinnamoyl andmaleimide undergo the "Class B" reaction.

With the Class A systems it is unnecessary to have any other lightabsorbing species present other than the polymerizable moiety, whilewith the Class B systems it is necessary to add to the system a speciescapable of initiating the polymer-forming or crosslinking reaction.However, with both classes certain "sensitizers" may be added. These"sensitizers" are species that can transmit the light energy they haveabsorbed to the polymerizable moiety in the Class A system or to thespecies capable of initiating the polymer-forming or crosslinkingreaction hereinafter termed "photoinitiator" in the Class B systems.This "sensitization" may be used advantageously in order to utilizelight sources that generally emit lower energy radiation; the latterlight sources are desirable in that they are less hazardous as far asaccidental exposure to eyes and skin are concerned and they are alsogenerally lower in cost. A more detailed account of "sensitizers" and"sensitization" is given in J. Kosar's text entitled Light SensitiveSystems: Chemistry and Application of Nonsilver Halide PhotographicProcesses (Wiley, 1964, pps. 5 and 185). Suitable sensitizers which maybe utilized in the invention are cited in J. F. Rabek's article entitled"Photosensitized Processes in Polymer Chemistry: a Review"(Photochemistry and Photobiology, 7, 5, (1960), and are hereinincorporated by reference. Also, suitable photoinitiators that can beadded to the Class B systems are cited in G. Oster and N. Yang's articleentitled "Photopolymerization of Vinyl Monomers" [Chem. Rev., 68, 125(1968)]. Examples of such initiators are acyloins and derivativesthereof, such as benzoin, benzoin methyl ether, benzoin ethyl ether,benzoin isopropyl ether and α-methylbenzoin; diketones such as benziland diacetyl, etc.; organic sulfides such as diphenyl sulfide, diphenyldisulfide, decyl phenyl sulfide and tetramethylthiurium monosulfide;S-acyl dithiocarbamates, such as S-benzoyl-N,N-dimethyldithiocarbamate,phenones such as acetophenone, α,α,α-tribromoacetophenone,α,α-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone,4'-nitro-2,2,2-tribromoacetophenone; benzophenone andp,p'-bis(dimethylamino)benzophenone; sulfonyl halides such asp-toluenesulfonyl chloride, 1-naphthalenesulfonyl chloride,2-naphthalenesulfonyl chloride, 1,3-benzenedisulfonyl chloride,2,4-dinitrobenzenesulfonyl bromide and p-acetamidobenzenesulfonylchloride. It is also contemplated that conventional heat activated freeradical catalysts such as organic peroxides and organic hydroperoxides,examples of which are benzoyl peroxide, tertiary-butyl perbenzoate,cumene hydroperoxide, azobis(isobutyronitrile) and the like, can be usedin the invention.

Where ultraviolet or visible radiation is used to achieve thecrosslinked insoluble polymers (VI) from the energy-sensitive polymers(V), suitable light sources include relatively low intensity lamps suchas germicidal, blacklight, and even sunlight exposure, and therelatively high intensity lamps such as mercury lamps, tungsten lamps,xenon arcs and the like. As is apparent to one skilled in the art, thereis an inverse relationship between exposure time and intensity ofactivating radiation. Thus, all of these light sources may be utilizedwith varying efficiencies in terms of length of exposure time toaccomplish the polymer-forming or cross-linking reaction.

Ionizing radiation may also be utilized as the activating radiation tobring about the crosslinking, insolubilizing reaction. The ionizingradiation can either be electromagnetic or particulate in nature.Electromagnetic ionizing radiation includes primarily X-ray and gammaradiation, while particulate ionizing radiation includes primarilyelectron and nuclear radiation. Suitable sources for ionizing radiationinclude resonance chambers, Van de Graff generators, betatrons,synchrotons, cyclotrons, atomic piles, radioactive isotopes, and thelike. While all of the various types of ionizing radiation can beutilized with the instant invention, the preferred ionizing radiationfrom economic and practical standpoints is the use of high energyaccelerated electrons.

The energy-sensitive elements of the invention are prepared by coating asubstrate with a solution of the energy-curable composition by anyconventional means such as dip coating, roll coating, air-knife coating,gravure coating, curtain coating, spray coating, use of wire woundcoating rods and the like. Typically, the substrate is coated with alayer that, after removal of solvent, has a thickness of about 10micrometers to 10 millimeters or thicker (thickness depending on purposeof use of the element) or about 1 to 1000 grams per square meter.

The coating solutions are prepared directly by in situ reaction ofazlactone polymer with the HXA compound. To this end, an azlactonecontaining interpolymer is dissolved typically at 10 to 50 percentsolids by weight in a solvent having no nucleophilic groups, i.e. ethylacetate, tetrahydrofuran, xylene and the like, or mixtures thereof. Tothis solution there is then added up to about 1.1 mole equivalents ofHXA nucleophilic compound per azlactone equivalent and about 0.1 to 5percent by weight of a Lewis acid based on polymer solids. The reactionsolution is agitated for 2 to 24 hours, preferably 2 to 8 hours, at 20°to 30° C., until the reaction is complete as evidenced by thedisappearance of the absorption band at about 5.4 microns in theinfrared spectrum of the reaction mixture. At this point additionalsolvent may be added to achieve a desirable viscosity with the coatingsolution. Suitable diluting solvents include lower alcohols, e.g.ethanol; lower esters, e.g. ethyl acetate; cyclic ethers, e.g.tetrahydrofuran; lower halocarbons, e.g. methylene chloride; and thelike.

For those articles that are to be prepared for use with visible orultraviolet radiation, a photoinitiator is added to the coatingcomposition. As previously discussed, photoinitiators suitable for usein the curable compositions of the invention are those compounds whichliberate or generate a free radical on addition of energy, examples ofwhich are given above. The purpose of these photopolymerizationinitiators in the practice of the present invention is to facilitatepolymerization when the composition is irradiated. Normally theinitiator is used in amounts ranging from about 0.01 to 5 percent byweight of the total polymerizable composition. When the quantity is lessthan 0.01 percent by weight, the polymerization rate becomes extremelylow. If the initiator is used in excess of 5 percent by weight, nocorrespondingly improved effect can be expected. Thus, addition of suchgreater quantity is economically unjustified. Preferably, about 0.5 to 2percent of initiator is used in the polymerizable compositions. The useof initiators is not necessary when curing is carried out with highenergy electrons.

As previously mentioned, compositions represented by Formulas V and VIare novel in the art as are the processes of their preparation,Equations D and E below. An overall schematic diagram resulting in theessential compositions of this invention is as follows: ##STR9##

The process and compositions involved in Formulas I through IV andEquations A through C are well known in the art. In the practice of thepresent invention amino acids (Formula I) suitable for use in thepreparation of the ethylenically unsaturated peptide carboxylic acidsare 2,2-disubstituted amino acids.

These are subjected to acylation (Equation A) with suitableethylenically unsaturated acylating agents resulting in thecorresponding ethylenically unsaturated peptide carboxylic acids. Theacylation with ethylenically unsaturated acylating agents such asacryloyl and methacryloyl chloride, shown in Equation A, is preformed inthe manner described by Kulkari and Morawetz, J. Polymer Sci., 54. 491(1961) by the portionwise addition of the acylating agent preferablycontaining a polymerization inhibitor such as hydroquinone or the likeand an equivalent amount of an acid absorber (e.g. aqueous sodiumhydroxide) to a vigorously stirred aqueous solution of an equivalentamount of an alkali metal salt of the amino acid at about 0° C.Generally a reaction time of 1 to 3 hours suffices to complete thereaction, after which the reaction mixture is neutralized with aqueousacid, such as 6 N HCl, and the ethylenically unsaturated peptidecarboxylic acid isolated.

Exemplary ethylenically unsaturated acylating agents include acryloylchloride, methacryloyl chloride, α-chloroacryloyl chloride, 3-butenoylchloride, 5-hexenoyl chloride, acryloyloxyacetyl chloride,methacryloyloxyacetyl chloride, 2-(acryloyloxy)propionyl chloride,3-acryloylthioxy)propionyl chloride 3-N-acryloyl-N-methylamino)propionyl chloride and the corresponding anhydrides.

The unsaturated peptide carboxylic acids thus formed can be used toprepare energy-sensitive polymers (Formula V) wherein n=1.

To prepare polymers of Formula V wherein n=2 requires use ofethylenically unsaturated azlactones, depicted by Formula III, asacylating agents to react with a suitable amino acid. Equation F showsthe preparation of an ethylenically unsaturated dipeptide carboxylicacid. ##STR10## wherein R⁴, R⁵, R⁶ and R⁷ are as previously definedabove for Formula V, R¹¹, R¹², R¹³ and R¹⁴ are the same as defined forR⁴, R⁵, R⁶ and R⁷ respectively.

A similar reaction, shown in Equation G, is used to prepareethylenically unsaturated tripeptide carboxylic acids. These acids arenecessary for the preparation of polymers of Formula V wherein n=3.##STR11## wherein R⁴, R⁵, R⁶, R⁷ are as defined above for Formula V andR¹¹, RHU 12, R¹³, R¹⁴ and R¹⁵, R¹⁶, R¹⁷, R¹⁸ are the same as R⁴, R⁵, R⁶,R⁷ respectively.

The formation of peptide units by the addition of amino acids toazlactone compounds is well known as the Bergmann azlactone peptidesynthesis (see for example K. Hubner et al., Angew. Makromol. Chemie,11, 109 (1970) and Bergmann et al., Ann., 449, 227 (1926).

The ethylenically unsaturated azlactone monomers, Formula IV, areprepared by the dehydration of the ethylenically unsaturated peptidecarboxylic acids just described in accordance with Equation C. Thisdehydration is carried out by stirring a mixture of the ethylenicallyunsaturated mono-, di- or tripeptide carboxylic acid and a dehydratingagent such as thionyl chloride, acetic anhydride ordicyclohexylcarbodiimide. A typical procedure involved dehydration withthe carbodiimide reagent at about 0°-50° C. for about 1-24 hours,preferably in an inert solvent such as methylene chloride, and apolymerization inhibitor. The reaction mixture is then filtered and thecyclized product recovered, preferably by distillation at reducedpressure.

Examples of suitable ethylenically unsaturated azlactone monomers(Formula IV) include:

2-vinyl-4,4-dimethyl-2-oxazolin-5-one,

2-isopropenyl-4,4-dimethyl-2-oxazolin-5-one,

2-vinyl-4,4-diethyl-2-oxazolin-5-one,

2-vinyl-4,4-dibutyl-2-oxazolin-5-one,

2-vinyl-4-methyl-4-nonyl-2-oxazolin-5-one,

2-vinyl-4-methyl-4-dodecyl-2-oxazolin-5-one,

2-isopropenyl-4-methyl-4-phenyl-2-oxazolin-5-one,

2-isopropenyl-4-methyl-4-benzyl-2-oxazolin-5-one,

2-vinyl-4,4-pentamethylene-2-oxazolin-5-one,

2-isopropenyl-4,4-tetramethylene-2-oxazolin-5-one,

2-allyl-4,4-dimethyl-2-oxazolin-5-one,

2-[2-(N-methacryloylamide)ethyl]-4,4-dimethyl-2-oxazolin-5-one,

2-(2-acryloylthioxy)ethyl-4,4-dimethyl-2-oxazolin-5-one,

2-vinyl-4,4-dimethyl-1,3-oxazin-6-one

2-(2-acryloyloxy)isopropyl-4,4-dimethyl-2-oxazolin-5-one.

2-vinyl-4,5,6,7-tetrahydro-4,4-dimethyl-1,3-oxazepin-7-one

The azlactone polymers (Formula IV) just described are converted to theethylenically unsaturated polymers of Formula V by reaction with freeradically polymerizable, ethylenically unsaturated nucleophiles,Equation D in the Schematic Diagram. The azlactone polymers (IV) mayalso be prepared by their interpolymerization with one or moreintermonomers using procedures generally known in the polymerization art(see, for example, K. Huebner et al., Angew. Makromol. Chem., 11, 109(1970)). Fairly standard free radical polymerization conditions areutilized with these monomers except that solvents such as alcoholicsolvents that could react with the azlactones by a ring opening additionreaction are to be avoided. Suitable solvents include ethyl acetate,toluene, xylene, acetone, methyl ethyl ketone, acetonitrile,tetrahydrofuran and the like, and combinations of these solvents.

Suitable free radical initiators for the polymerization reaction includeazobis(isobutyronitrile), benzoyl peroxide, t-butyl hydroperoxide andthe like.

Intermonomers suitable for interpolymerization with the ethylenicallyunsaturated azlactone monomers include essentially any free radicallypolymerizable ethylenically unsaturated monomers except those of the HXAtype which have been previously described because these monomers causean undesirable premature insolubilization of the interpolymer. Examplesof suitable intermonomers include the vinyl aromatic monomers such asstyrene, α-methylstyrene, 2- and 4-vinylpyridine, and the like;α,β-unsaturated carboxylic acids such as acrylic acid, methacrylic acid,itaconic acid, maleic acid, fumaric acid, crotonic acid, and the like;α,β-unsaturated carboxylic acid derivatives such as methyl methacrylate,butyl methacrylate, 2-ethylhexyl methacrylate, ethyl acrylate, butylacrylate, iso-octyl acrylate, octadecyl acrylate, cyclohexyl acrylate,tetrahydrofurfuryl methacrylate, phenyl acrylate, phenethyl acrylate,benzyl methacrylate, β-cyanoethyl acrylate, maleic anhydride, diethylitaconate, acrylamide, methacrylonitrile, N-butylacrylamide and thelike; vinyl esters of carboxylic acids such as vinyl acetate, vinyl2-ethylhexanoate and the like; vinyl halides such as vinyl chloride,vinylidene chloride and the like; vinyl alkyl ethers such as methylvinyl ether, 2-ethylhexyl vinyl ether, butyl vinyl ether and the like;olefins such as ethylene; N-vinyl compounds such as N-vinylpyrrolidone,N-vinylcarbazole and the like; vinyl ketones such as methyl vinyl ketoneand the like; and vinyl aldehydes such as acrolein, methacrolein and thelike. The preferred intermonomers in the present invention are theα,β-unsaturated carboxylic acid derivatives. As is apparent to oneskilled in the art, the above intermonomers can be utilized with theazlactone monomers alone or, as is often desirable, combinations of theabove intermonomers can be utilized. The overall objective offormulation of the various intermonomers with the azlactone monomersthat are subsequently reacted with the HXA compound is generally toobtain a polymer film that can be handled and imaged easily in thenon-crosslinked form prior to treatment with the activating radiation.

As previously described, the azlactone polymers of Formula IV may beconverted to the compositions of the invention, polymers of Formulas Vand VI, by means of reactions described by Equations D and E.

The compositions of the invention can also include a variety of addendautilized for their known purpose, such as stabilizers, inhibitors,lubricants, flexibilizers, pigments, dyes, reinforcing fillers such asfinely divided silica, non-reinforcing fillers such as diatomaceousearth, metals, metal oxides, asbestos, fiberglass, glass bubbles, talc,etc. Where the polymerizing energy is electromagnetic radiation, it isdesirable that the addenda be transparent to the radiation.

It is also contemplated as being within the scope of the invention thatreactive diluents such as methyl methacrylate, ethylene diacrylate,hexanediol diacrylate, trimethylolpropane triacrylate, pentaerythritoltetracrylate and the like may be added advantageously to improve therate and degree of the radiation induced crosslinking reaction.

The photocurable elements are particularly suitable for applications inthe field of graphic arts because of their capability for forming highresolution images. Among such uses are solvent-developable resists forchemical milling, gravure images, offset plates, stencil making,screenless lithography, relief printing plates and printed circuits, andthe like.

The invention is further illustrated by the following examples.

PREPARATION OF 2-ETHYLENICALLY UNSATURATED AZLACTONE MONOMERS (a)Preparation of amino acids

1. Synthesis of hydantoin

Sodium cyanide (55 grams, 1.412 moles) and ammonium carbonate (96 grams,3,253 moles) were dissolved in 1235 milliliters of water. 2-Undecanone(170 grams, 0.588 mole) dissolved in 1235 milliliters of ethanol wasadded, resulting in precipitation of a fine white solid. The mixture wasstirred at room temperature for 4 hours and at 45° C. for 18 hours.Water (3500 milliliters) was added to the ivory colored suspension, andthe mixture was filtered. The filter cake was washed well with water anddried. Yield: 138.9 grams (98 percent of theoretical) of5-methyl-5-nonylhydantoin; melting range: 104°-106° C.

By substituting other ketones for 2-undecanone in the above reactionother 5,5-dialkylhydantoins were prepared.

2. Hydrolysis of hydantoin to the corresponding amino acid

The hydantoin prepared above (133 grams, 0.55 mole) was suspended in1110 milliliters of 48 percent hydrobromic acid and refluxed gently for18 hours. After cooling, the hydrobromic acid was removed at reducedpressure using a rotary evaporator. The solid residue remaining wasdissolved in 660 milliliters of aqueous methanol (90 volume percentmethanol), and the pH was adjusted to 6.5 with concentrated ammoniumhydroxide. The resulting slurry was poured into 3500 milliliters ofacetone, the resulting flocculent white solid collected by filtrationand washed well with water and acetone. The nonylalanine obtained wasfurther purified by recrystallation from methanol-water. Yield: 115grams (97 percent); melting point: 264° C. (sealed tube).

By substituting other 5,5-dialkylhydantoins in the above reaction otheramino acids were prepared. Many amino acids are available commerciallyand were used when practical in preparing the compositions and elementsof the invention.

(b) Acylation of amino acids to form ethylenically unsaturatedcarboxylic acids

Methylalanine (103 grams, 1.00 mole) was added to 40 grams (1 mole) ofsodium hydroxide dissolved in 350 milliliters of water. Acryloylchloride (86 grams, 0.95 mole) and sodium hydroxide (38 grams, 0.95mole) dissolved in 75 milliliters of water were then added dropwise,each from their own dropping funnel, to the stirred reaction solutionover the course of 30 minutes such that the reaction temperature did notexceed 5° C. The reaction solution was stirred an additional 10 minutesafter the addition before acidification to pH 2 with concentratedhydrochloric acid. The white powder precipitate ofN-acryloylmethylalanine was collected by filtration, washed well withwater and dried. Yield: 131.5 grams (88 percent); melting point:185°-186.5° C.

In a similar manner other ethylenically unsaturated peptide carboxylicacids were prepared by substituting other amino acids for methylalaninein the above reaction.

(c) Dehydration of ethylenically unsaturated peptide carboxylic acids toform azlactone monomers

Finely divided N-acryloylmethylalanine (33 grams, 0.21 mole) was addedto a stirred mixture of dicyclohexylcarbodiimide (41.2 grams, 0.2 mole)dissolved in 500 milliliters of methylene chloride. The reaction mixturewas then stirred at 25° C. overnight. The dicyclohexylurea and slightexcess of the N-acryloylmethylalanine employed were filtered, and thefiltrate evaporated in vacuo. The light brown oily residue was thendistilled at reduced pressure with a water-white fraction distilling at63°-67° C. at 25 mm. pressure being collected. Yield: 22.8 grams (82percent) of 2-vinyl-4,4-dimethyl-2-oxazolin-5-one.

By replacing N-acryloylmethylalanine with other unsaturated peptidecarboxylic acids in the above reaction other azlactone monomers wereobtained.

(d) Polymerization of azlactone monomers to form azlactone polymers

Into a reaction vessel equipped with a stirrer, thermometer, refluxcondenser, means for heating and means for maintaining a nitrogenatmosphere in the vessel were charged

    ______________________________________                                        2-vinyl-4,4-dimethyl-2-oxazolin-5-one                                                                 50       parts                                        ethyl acetate           75       parts                                        azobis(iso-butyronitrile)                                                                             0.15     parts                                        ______________________________________                                    

The solution was sparged with nitrogen and heated at 55° C. withagitation for 24 hours. After this time, the percent polymer solids inthe solution obtained, as determined by a standard gravimetricprocedure, was 37.9 percent and the inherent viscosity as measured inacetone (0.20 gram of polymer dissolved in 100 milliliters of acetone)and 30° C. was 0.82 deciliters per gram, corresponding to a weightaverage molecular weight of about 300,000.

In a similar manner other azlactone monomers or mixtures with one ormore other intermonomers were polymerized. Table I lists variousazlactone polymers that have been prepared

                  TABLE I                                                         ______________________________________                                        Azlactone Polymer(a)   Viscosity(c)                                           (ratio(b) of monomers) (<n>)                                                  ______________________________________                                        VDM                    0.82(d)                                                MM-VDM (90:10)         0.62                                                   MM-VDM (80:20)         0.68                                                   BA-VDM (50:50)         0.21(d)                                                ST-VDM (60:40)         0.34                                                   BA-IDM (50:50)         0.06                                                   n-BMA-VMN (65:35)      0.36                                                   i-BMA-n-BMA-VDM (54:20:26)                                                                           0.46                                                   MM-VA-MA-BVE-VMP (50:10:2.5:2.5:35)                                                                  0.44                                                   n-BMA-BA-VDM (80:10:10)                                                                              0.35                                                   IOA-AM-VDM (55:5:40)   0.35                                                   EA-NVP-VTM (55:10:35)  0.89                                                   BMA-VDM (60:40)        0.20                                                   i-BMA-BA-VDM (20:40:40)                                                                              0.12                                                   BMA-IDM (60:40)        0.07                                                   MM-VDM(6) (65:35)      0.50                                                   ______________________________________                                         Notes:-                                                                       (a)Abreviations used for monomeric components of the azlactone polymers       are:                                                                          VDM                                                                           MM methyl methacrylateoxazolin-5-one-                                         BA butyl acrylate                                                             ST styrene                                                                    VA vinyl acetate                                                              AM acrylamide                                                                 VMN                                                                           iBMA isobutyl methacrylateoxazolin-5-one-                                     nBMA nbutyl methacrylate                                                      IDM                                                                           IOA isooctyl acrylatethyl-2-oxazolin-5-one-                                   BVE butyl vinyl ether                                                         EA ethyl acrylate                                                             NVP Nvinylpyrrolidone-                                                        VTM                                                                           MA maleic anydridethylene-2-oxazolin-5-one-                                   VDM(6)                                                                        (b)All ratios are on a weightweight basis.                                    (c) Unless otherwise stated, all inherent viscosities were measured using     0.15 g. of polymer/100 ml. of tetrahydrofuran.                                (d)Viscosity was measured using 0.20 g. polymer/10 ml. of solvent.       

EXAMPLE 1 Reaction of azlactone polymers with HXA nucleophilic agents toform energy-curable polymers having pendant ethylenically unsaturatedpeptide groups

To 13.3 grams of a tetrahydrofuran:ethyl acetate (1:2.3) solution of then-butylacrylate:2-vinyl-4,4-dimethyl-2-oxazolin-5-one (50:50)interpolymer, designated BA-VDM (50:50) containing 5.3 grams of theinterpolymer having 0.019 mole of pendant azlactone was added 2.5 grams(0.019 mole) of 2-hydroxyethyl methacrylate and 5 drops of BF₃ etherate.After stirring for 3 hours at 25° C., the reaction was complete asevidenced by the disappearance of the carbonyl stretching absorptionband at about 5.4 microns in the infrared spectrum. Removal of thesolvent produced a tack-free, energy-curable polymer having pendantmethacryloyl peptide groups, designated BA-VDM (50:50)/HEMA.

In a similar manner other polymers of azlactone monomers andinterpolymers of azlactone monomers with intermonomers were caused toreact with various HXA agents to form various energy-curable,ethylenically unsaturated peptide group-containing polymers and coatingsolutions of the invention.

EXAMPLE 2 Preparation of Energy Sensitive Elements

A coating solution was prepared by dissolving 0.3 gram of Irgacure 651(2,2-dimethoxy-2-phenylacetophenone, available from Ciba-Geigy) in asolution prepared as in Example 1 consisting of 30 grams of BA-VDM(50:50)/HEMA in 70 grams of ethyl acetate. The solution was then coatedonto 100 micrometer polyester film using a No. 32 wire-wound coatingrod. On air drying, a tack-free layer having a thickness of about 25micrometers was obtained.

A metal image template was placed on the tack-free film, and thecomposite was exposed to activating radiation. Three different radiationconditions were utilized:

Condition 1:

The composite was exposed in a nitrogen blanketed atmosphere for oneminute to a medium pressure mercury lamp through 1/8 inch Pyrex glasswith a lamp-to-composite distance of 20 cm.

Condition 2:

The composite was exposed for one minute to a medium pressure mercurylamp in air with a lamp-to-composite distance of 15 cm.

Condition 3:

The composite was exposed to electron beam radiation using theELECTROCURTAIN apparatus operated at 225 kilovolts with the various doserates given in megarads (MR) designated in parentheses. TheELECTROCURTAIN apparatus is a linear cathode unit available from EnergySciences, Inc., Bedford, Mass.

The exposed composite film was then allowed to soak in ethyl acetate toremove the non-exposed areas. The resultant image, when dry, hadexcellent resolution, showing sharp differentiation between exposed andnonexposed areas.

EXAMPLES 3-19

Example 2 was repeated using in palce of BA-VDM (50:50)/HEMA the variouspolymers having pendant ethylenically unsaturated peptide groups andexposure conditions shown in Table 2. The quality of the image obtainedfor each of the energy-curable constructions is also shown.

                  TABLE II                                                        ______________________________________                                                                    Imaging  Image                                    Ex.  Energy-curable         Condi-   Qua-                                     No.  Polymer (d)/HXA(e)     tion(f)  lity(g)                                  ______________________________________                                        2    BA-VDM (50:50)/HEMA    2        exc                                      3    VDM(100)/HEMA          1        exc                                      4    MM-VDM(90:10)/HEMA(h)  1        un                                       5    MM-VDM(90:10)/HEMA     1        exc                                      6    MM-VDM(80:20)/HEMA     1        exc                                      7    i-BMA-n-BMA-VDM(54:20:26)/HEMA                                                                       2        exc                                      8    EA-NVP-VTM(55:10:35)/HEMA                                                                            2        exc                                      9    i-BMA-n-BMA-VDM(54:20:26)/HPA                                                                        3 (2MR)  exc                                      10   IOA-AM-VDM(55:5:40)/OD 3 (4MR)  exc                                      11   ST-VDM(60:40)/HEMA     2        exc                                      12   BA-IDM(50:50)/HEMA     2        exc                                      13   n-BMA-VMN(65:35)/HEMA  2        exc                                      14   MM-VA-MA-BVE-VMP(50:10:2.5:                                                   2.5:35)/HEMA           2        exc                                      15   n-BMA-BA-VDM(80:10:10)/PETrA                                                                         2        exc                                      16   i-BMA-n-BMA-VDM(54:20:26)/AlM                                                                        2        ma                                       17   BA-VDM-(50:50)/MEA-FMMEE                                                                             2        exc                                      18   i-BMA-n-BMA(54:20:26)/HBVE                                                                           2        exc                                      19   BA-IDM(50:50)/MAlAM    2        exc                                      20   n-BMA-VDM(60:40)/HEMA  2        exc                                      21   i-BMA-BA-VDM(20:40:40)/HEMA                                                                          2        exc                                      22   n-BMA-IDM(60:40)/HEMA  2        exc                                      23   MM-VDM(6) (65:35)/HEMA 2        exc                                      ______________________________________                                         Notes:                                                                        (d)Monomeric components of polymer are the same as defined in Table 1.        (e)Abbreviations for the ethylenically unsaturated nucleophilic agents        used in forming the ethylenincally unsaturated peptide group of the           polymer are:                                                                  HBVE  4hydroxybutyl vinyl ether                                               HEMA  2hydroxyethyl methacrylate                                              HEP  3hydroxypropyl acrylate                                                  PETrA  pentaerylthritol triacrylate                                           AlM  allylmercaptan                                                           MEAFMMEE  adduct of 2mercaptoethanol and fumaric acid monoethyl               OD  9octadecen-1-ol                                                           MAlAM  methallylamine                                                         (f)Exposure condition described in Exhibit 2.                                 (g)Image quality: exc is exceptional, ma is marginally acceptable and un      is unacceptable.                                                              (h)Only 50 mole percent of the azlactone group of the azlactone polymer       was reacted with the HXA compound.                                       

What is claimed is:
 1. A composition comprising a radiation-curablepolymer, said polymer being crosslinkable and having pendantethylenically unsaturated peptide groups and the following structuralformula ##STR12## wherein M is a unit from one or more free radicallypolymerizable ethylenically unsaturated monomers;R¹ is hydrogen ormethyl; R² is selected from a single bond, --R³ -- and ##STR13## inwhich R³ is alkylene having 1 to 12 carbon atoms, preferably 1 to 6carbon atoms, and W is --O--, --S-- or --NH--; R⁴ and R⁷ areindependently selected from a single bond and methylene, or substitutedmethylene having 1 to 12 carbon atoms; R⁵ and R⁶ are independently alkylor cycloalkyl having 1 to 12 carbon atoms, aryl or aralkyl having 6 to12 carbon atoms or R⁵ and R⁶ taken together with the carbon to whichthey are joined form a 5- or 6-membered carbocyclic ring, or may be Hwhen at least one of R⁴ and R⁷ is methylene; n is 1, 2 or 3; X is --O--,--NH-- or --S--; A is a polymerizable, ethylenically unsaturated groupselected from(a) ##STR14## in which R⁸ is an alkylene group having 1 to12 carbon atoms, an arylene group having 1 to 12 carbon atoms, anarylene group having 6 to 10 carbon atoms, or an oxyalkylene group,--OR--_(p) in which R is a lower alkylene group having 2 to 4 carbonatoms and p is 1 to 4; R⁹ and R¹⁰ are independently hydrogen, an alkylgroup having 1 to 12 carbon atoms, or an aryl group having 6 to 10carbon atoms or (b) --R⁸ WY in which R⁸ is as defined under thedefinition for A, W as defined under the definition for R², and Y is anethylenically unsaturated acyl group selected from the group includingacryloyl, methacryloyl, cinnamoyl, maleoyl, fumaroyl, itaconoyl andcrotonoyl; a and b are independent whole integer numbers, and b is atleast 1, sufficient to provide a polymer wherein the distribution of Munits and ##STR15## units is random throughout the polymer.
 2. Thecomposition according to claim 1 wherein A is --R⁸ WY and Y is selectedfrom the class of acryloyl and methacryloyl units.
 3. The compositionaccording to claim 1 wherein said polymer comprises at most 90 percentby weight of "M" units.
 4. The composition according to claim 1 whereinsaid polymer comprises at most 75 percent by weight of "M" units.
 5. Thecomposition according to claim 1 wherein said polymer comprises at most70 percent by weight of "M" units.
 6. The composition according to claim1 wherein said polymer comprises at least 10 weight percent of unitsderived from ethylenically unsaturated azlactone monomers.
 7. Thecomposition according to claim 1 wherein said polymer comprises at least25 weight percent of units derived from ethylenically unsaturatedazlactone monomers.
 8. The compositions according to claim 1 whereinsaid polymer comprises at least 30 weight percent of units derived fromethyylenically unsaturated azlactone monomers.
 9. The compositionaccording to claim 1 wherein said polymer is radiation-curable in air.10. The composition according to claim 1 wherein said polymer is derivedfrom(a) one or more "M" monomers selected from the group consistingofbutyl acrylate, methyl methacrylate iso-butyl methacrylate, n-butylmethacrylate, ethyl acrylate, N-vinylpyrrolidone, iso-octyl acrylate,acrylamide, styrene, vinyl acetate, maleic anhydride, butyl vinyl ether,(b) an azlactone monomer selected from the group consistingof2-vinyl-4,4-dimethyl-2-oxazolin-5-one,2-vinyl-4,4-tetramethylene-2-oxazolin-5-one,2-isopropenyl-4,4-dimethyl-2-oxazolin-5-one,2-vinyl-4-methyl-4-nonyl-2-oxazolin-5-one,2-vinyl-4-methyl-4-phenyl-2-oxazolin-5-one,2-vinyl-4-methyl-4-phenyl-2-oxazolin-5-one,2-vinyl-4,5-dihydro-4,4-dimethyl-1,3-oxazin-6-one2-vinyl-4,5,6,7-tetrahydro-4,4-dimethyl-1,3-oxazepin-7-one (c) and HXAunits selected from the group consisting of2-hydroxyethyl methacrylate,3-hydroxypropyl acrylate, 9-octadecen-1-ol, pentaerythritol triacrylate.11. The composition according to claim 1 wherein the weight ratio of "M"units to peptide units is between 9:1 and 0:10, respectively.
 12. Thecomposition according to claim 1 further containing a solvent.
 13. Thecomposition according to claim 12 wherein the polymer is dissolved in asolvent such that the solution contains approximately 10-50 percent byweight of the polymer.
 14. The method of preparing a radiation-curablepolymer, said polymer being crosslinkable and having pendantethylenically unsaturated peptide groups and the following structuralformula ##STR16## wherein M is a unit from one or more free radicallypolymerizable ethylenically unsaturated monomers;R¹ is hydrogen ormethyl; R² is selected from a single bond, --R³ -- and ##STR17## inwhich R³ is alkylene having 1 to 12 carbon atoms, preferably 1 to 6carbon atoms, and W is --O--, --S-- or NH--; R⁴ and R⁷ are independentlyselected from a single bond and methylene, or substituted methylenehaving 1 to 12 carbon atoms; R⁵ and R⁶ are independently alkyl orcycloalkyl having 1 to 12 carbon atoms, aryl or aralkyl having 6 to 12carbon atoms or R⁵ and R⁶ taken together with the carbon to which theyare joined form a 5- or 6-membered carbocyclic ring, or may be H when atleast one of R⁴ and R⁷ is methylene; n is 1, 2 or 3; X is --O--, --NH--or --S--; A is a polymerizable, ethylenically unsaturated group selectedfrom(a) ##STR18## in which R⁸ is an alkylene group having 1 to 12 carbonatoms, an arylene group having 1 to 12 carbon atoms, an arylene grouphaving 6 to 10 carbon atoms, or an oxyalkylene group, --OR--_(p) inwhich R is a lower alkylene group having 2 to 4 carbon atoms and p is 1to 4; R⁹ and R¹⁰ are independently hydrogen, an alkyl group having 1 to12 carbon atoms, or an aryl group having 6 to 10 carbon atoms or (b)--R⁸ WY in which R⁸ is as defined under the definition for A, W asdefined under the definition for R², and Y is an ethylenicallyunsaturated acyl group selected from the group including acryloyl,methacryloyl, cinnamoyl, maleoyl, fumaroyl, itaconoyl and crotonoyl; aand b are independent whole integer numbers, and b is at least 1,sufficient to provide a polymer wherein the distribution of M units and##STR19## units is random throughout the polymer, which method includesthe steps of a. blending together in a non-nucleophilic solvent(1) anethylenically unsaturated nucleophilic compound of the formula HXAwhereinH is hydrogen; X is --O--, --NH-- or --S--; A is a polymerizable,ethylenically unsaturated group selected from (a) ##STR20## in which R⁸is an alkylene group having 1 to 12 carbon atoms, an arylene grouphaving 6 to 12 carbon atoms, or an oxyalkylene group, --OR--_(p) inwhich R is a lower alkylene group having 2 to 4 carbon atoms and p is 1to 3; R⁹ and R¹⁰ are independently hydrogen, an alkyl group having 1 to12 carbon atoms, or an aryl group having 6 to 10 carbon atoms or (b)--R⁸ --WY in which R⁸ is as defined under the definition for R², and Yis an ethylenically unsaturated acryl group selected from the groupincluding acryloyl, methacryloyl, cinnamoyl, maleoyl, fumaroyl,itaconoyl and crotonoyl, and (2) a polymer having pendant azlactonegroups, said polymer resulting from interpolymerization of(a) 10 to 100percent by weight of units from one or more ethylenically unsaturatedazlactone monomers, and (b) 90 to 0 percent by weight of one or morevinyl monomers, and (3) 0 to 5 percent by weight of a Lewis acidcatalyst and b. reacting components (1) and (2).